Patrick & Atsugi have given you good advice. If you are not financially strapped, a combination of regular Medicare (Parts A & B) and a supplement (such as those endorsed by AARP and issued by United Health Care) may provide the best coverage for you. There are several plans, depending on what you can afford. The supplements may or may not include Part D, prescription drug coverage.
For those of us who are financially limited, a Medicare Advantage Plan may still be the best option, although I think the government is trying to phase them out. Medicare Advantage Plans are issued by private insurers and follow Medicare guidelines, but usually pay better than original Medicare. Most have an annual out-of-pocket maximum. Social Security sends the money withheld from a person's monthly Social Security check ($104.90 for 2014) to the private insurer to be applied to the monthly health ins. premium. Most of these plans include Part D. Plans can be compared on line at Medicare.gov. Be sure to have a list of all prescription medications handy before visiting the site, as you will need to enter all of them to get accurate cost information. Be sure to look at co-pay amounts, deductibles, and payment percentages for durable medical equipment as well as annual out-of-pocket limits. The better plans require a monthly premium payment in addition to the $104.90 from Social Security but are usually still less costly than original Medicare plus a supplement.
Good Luck!